Photoresists of the initially named type have already been known for a long time and are described, for example, in U.S. Pat. Nos. 30,957,512, 4,040,831, 4,548,891 or EP-A-0 624,826 (U.S. patent application Ser. No. 08/524,648). In the named photoresist compositions, the residue R represents all organic residues with a photopolymerizable olefinic double bond, so that the compositions are cross-linked by the action of radiation of suitable wavelength via the photopolymerizable olefinic double bonds in the photoreactive polyimide precursor. The named negative resists have a very high sensitivity and show only very small dark removal [stripping] in development. Further, they have the advantage that a coating produced with their help can be converted into a polyimide coating by curing after exposure and development, whereby the coating is particularly heat-resistant. However, it is a disadvantage that such negative resists up to now have had to be treated with developers that are practically completely comprised of organic solvents, which, of course, is undesirable, due to the expenditure associated therewith for environmentally friendly disposal, and due to their inflammability.
In ACS Polym. Prep. Vol. 33 (1), April 1992, Rumiko Hayase et al. describe positively operating photoresist compositions comprised of 80 weight percent of a polyimide precursor of the above formula (I), in which R represents a 2-hydroxybenzyl residue, and 20 weight percent of a naphthoquinone diazide compound, as is usually used as a radiation-sensitive solution inhibitor for conventional positive photoresists. For the development of the named positive resists, developers can be used, in fact, which are comprised predominantly of common aqueous-alkaline developer solutions for photoresists, e.g., an aqueous tetramethylammonium hydroxide solution, but these solutions must still contain a considerable portion of methanol (approximately 12 volumetric percent), so that a sufficiently high rate of dissolution of the resist material in the developer is assured. In addition, the named positive photoresists show a relatively high dark stripping and lead to problems with process stability.
The object of the present invention is to make available a negatively operating photoresist composition based on polyimide precursors of the above-named formula (I), which permit the use under common practice conditions of conventional, e.g., commercially available, aqueous-alkaline developers, which are free of organic solvents.